New crop of plug-in vehicles appearing in Los Angeles as cheap gasoline makes the sell tougher

The coming weeks offer big new showcases for the humble electric-vehicle.

Auto makers, rushing to meet tightening emissions standards, are unveiling new battery-powered vehicles at the Los Angeles Auto Show this week, mirroring last month’s flood of such cars by European companies. These curtain-raisers will be followed by first shipments of General Motors Co.’s Chevrolet Bolt, a $35,000 Tesla fighter that goes on sale next month....